exception_handling_exercises.py

# ==========================================
# Python Learning Lab: 08 Exception Handling
# ==========================================

print("--- Running Exception Handling Exercises ---")

# ==========================================
# Challenge 1: Handling Exceptions (try-except-finally)
# ==========================================
# Write a function that converts a string to an integer and divides 100 by it.
# Handle:
# - ValueError: if the string cannot be converted to an integer. Return -1.
# - ZeroDivisionError: if the input is "0". Return -2.
# Use a finally block to append the message "Checked" to `status_list`.

status_list = []

def safe_divide(val_str):
    # TODO: Implement exception handling and finally block
    try:
        num = int(val_str)
        return 100 / num
    except ValueError:
        return -1
    except ZeroDivisionError:
        return -2
    finally:
        status_list.append("Checked")

# --- Verification ---
status_list.clear()
assert safe_divide("5") == 20.0, "Valid division failed"
assert status_list == ["Checked"], "Finally block not executed for success"

status_list.clear()
assert safe_divide("abc") == -1, "Should catch ValueError and return -1"
assert status_list == ["Checked"], "Finally block not executed for ValueError"

status_list.clear()
assert safe_divide("0") == -2, "Should catch ZeroDivisionError and return -2"
assert status_list == ["Checked"], "Finally block not executed for ZeroDivisionError"
print("✓ Challenge 1 passed!")


# ==========================================
# Challenge 2: Custom Exceptions
# ==========================================
# 1. Define a custom exception class `NegativeNumberError` inheriting from `Exception`.
# 2. Complete the function `calculate_square_root` to raise `NegativeNumberError` if the input is negative.

# TODO: Define NegativeNumberError
class NegativeNumberError(Exception):
    pass

def calculate_square_root(num):
    # For now, let's just return math.sqrt(num) if it's positive.
    # TODO: Raise NegativeNumberError if num < 0
    if num < 0:
        raise NegativeNumberError("Number cannot be negative!")
    return num ** 0.5

# --- Verification ---
assert calculate_square_root(9) == 3.0, "Square root calculation failed"

try:
    calculate_square_root(-4)
    assert False, "Should raise NegativeNumberError"
except Exception as e:
    # If the custom exception is implemented, check if it's correct
    assert e.__class__.__name__ == "NegativeNumberError", f"Expected NegativeNumberError, got {e.__class__.__name__}"
    print("✓ Challenge 2 passed!")

print("\n🎉 All tests passed successfully!")